1. Field of the Invention
The present invention relates to a method for isolating and purifying nucleic acids by eluting nucleic acids from nucleic acid-containing samples, such as biological materials.
2. Description of Related Art
An efficient method known in the art for isolating and purifying nucleic acids is based on the adsorption of the nucleic acids on glass or silica particles in the presence of a chaotropic salt, followed by recovering the nucleic acids (Vogelstein, B. and Gillespie, D. (1979); “Preparative and analytical purification of DNA from agarose”, Proc. Natl. Acad. Sci. USA 76: 615–619). According to this method and using high concentrations of a chaotropic salt, such as sodium iodide, sodium perchlorate or guanidine thiocyanate, DNA can be isolated and purified from agarose, or RNA or DNA can be isolated and purified from various mixtures (Boom, R. (1990); Rapid and simple method for purification of nucleic acids, J. Clin. Microbiol. 28: 495–503).
Nucleic acids after purification are often subjected to the polymerase chain reaction (PCR). The technique of PCR amplifies nucleic acids in a sequence-specific manner and therefore is widely used in genetic or DNA diagnosis. In utilizing this PCR technique routinely for clinical purposes, several problems arise. It is known, among others, that inhibitor substances remaining un-removed in the nucleic acids purification step inhibit the PCR. Such inhibitor substances include hemoglobin and surfactants used in the nucleic acids extraction process, for instance. With such a background, it is pointed out that the processes for extracting and purifying nucleic acids are important (Oshima et al., JJCL A, 22(2), 145–150 (1997)).
The procedures in the extracting process which have so far been carried out manually are complicated and requires skills. As such, automation by instruments is desired. Thus, it is demanded that an extraction method suitable for automation be developed, inclusive of reagents to be used. There is a nucleic acids extraction method suitable for automation described in JP-A-127854/1999, and another method using the apparatus described in JP-A-266864/1999. Further, there are reagents allegedly suitable for nucleic acids extraction on an automated apparatus described in Tokuhyo (Japanese Translation of Unexamined PCT Appln.) No. 501321/1996. According to the method using the reagents described in the Tokuhyo No. 501321/1996, the nucleic acids to be isolated and purified from a solution containing a high concentration (ionic strength) of salts and a high concentration of alcohol are brought into contact with an adsorption support within a column for genome extraction so as to adsorb them on the support then desorb them from the adsorption support by means of a solution containing lower concentration (ionic strength) of salts.
However, the method for isolating and purifying nucleic acids using the reagents described in the Tokuhyo No. 501321/1996 has a problem in that the yield of nucleic acids collection is low. The method, which uses the column for genome extraction described in JP-A-127854/1999, requires a long period of time for contacting the nucleic acids with the adsorption support to adsorb them thereon, since the viscosity of the solution is high.